Tweaks to table display

Increase padding of <hr> element
Add @viewport rule

I don't think this is currently supported by anything but it's nice to dream.
W3C draft here: http://dev.w3.org/csswg/css-device-adapt/

In the meantime, in order for this stylesheet to show properly in iOS devices,
you'll still have to put this in the HTML header:

<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />